Hydraulic recoil absorber for shoulder-fired firearms



J. M. AHEARN Feb. 8, 1966 HYDRAULIC RECOIL ABSORBER FOR SHOULDER-FIRED FIREARMS 2 Sheets-Sheet 1 Filed Aug. 14, 1964 INVENTOR.

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J. M. AHEARN Feb. 8, 1966 HYDRAULIC RECOIL ABSORBER FOR SHOULDER-FIRED FIREARMS Filed Aug. 14, 1964 2, Sheets-Sheet 2 INVENTOR. uo/m/ /4 Ava 542M United States Patent 3,233,354 HYDRAULIC RECOIL ABSORBER FOR SHQULDER-FIRED FIREARMS John M. Ahearn, 1920 SW. 86th Ave., Miami, Fla. Filed Aug. 14, 1964, Ser. No. 389,596

3 Claims. (ill. 42-74) This invention relates to a hydraulic recoil absorber, especially but not exclusively, for shoulder-fired firearms.

The primary object of the invention is the provision of a device of the kind indicated, and its incorporation in a firearm, which obtains the following and other desirable results:

(a) Non-violent operation, in both recoil and reset ac tions, or" the device, thereby reducing the shock to the shooter and enabling better control of the firearm, as in rapid fire;

(b) Mechanical adjustability of the device to compensate for length of pull of the firearms; and automatic adjustment to compensate for expansion and contraction of the hydraulic fluid in the device due to changes of temperature, without changes in the adjusted length of pull;

(0) Absence of hydraulic fluid under pressure in the device, except at the moment of firing, and then only in an area where no scaling is required which would otherwise require extensive pressure sealing and subject the device to leakages of hydraulic fluid under service conditions;

(d) Return of the piston, after recoil absorption, only by light return spring means, rather than by hydraulic pressure, thereby eliminating the shock producing effects inherent in related devices operating under high hydraulic initial or starting pressures followed by high hydraulic pressure return of the piston;

(e) Simplified construction, making for a small number of simple and easily assembled parts, and easy servicing.

In the drawings:

FTGURE 1 is a fragmentary side elevation of a firearm stock containing a device of the present invention;

FIGURE 2 is an enlarged vertical transverse section taken on the line 22 of FIGURE 1;

FIGURE 3 is a fragmentary longitudinal section, on the scale of FIGURE 2, taken on the line 3-3 of FIGURE 2;

FIGURE 4 is a fragmentary longitudinal section taken on the line 44 of FIGURE 3;

FIGURE 5 is a transverse section taken on the line 5-5 of FIGURE 4;

FIGURE 6 is an enlarged perspective view or" the device, parts being broken away and in section, the piston of the device being shown in starting position;

FIGURE '7 is a perspective view of the fluid orifice cylinder; and

FIGURE 8 is a fragmentary side elevation of another embodiment of the invention.

Referring in detail to the drawings, and first to P16- URES l to 7, thereof, there is shown a firearm having a two-piece stock, consisting of a solid forepiece or first member 10 and a tubular rear or butt piece or second member 12, which slides over the forepiece it), and has a longitudinal blind bore 14 which opens to the forward end of the butt piece, and has a flat rear end 16.

A preferably rectangular anchor plate 18 is suitably fixed in an accommodating recess 20, formed in the bore 3,233,354 Patented Feb. 8, 1966 end 16. Upper and lower longitudinal, parallel spaced guide rods 22 extend forwardly from the anchor plate 18 and are threaded therein, at their rear ends, as indicated at 24, at equal distances from the center of the plate 18, whereat a threaded bore 26 is formed. The guide rods 22 slide in swivelly aligned bores 28 formed in and opening to the fiat rear end 30 of the stock forepicce it).

A piston rod 32 extends forwardly from the anchor plate 18 and has a relatively long threaded'rear end portion 34, which is adjustably threaded through the bore 26 of the anchor plate, and is provided with an adjustment fixing lock nut 36, which bears against the rear side of the anchor plate. A fluid bore 38 is provided in the rear end 16 of the butt piece 12, to accommodate the lock nut and the rear end of the piston rod 32;

On a line with the piston rod 32, the forepiece it is formed with an enlarged diameter longitudinal blind bore 40, in which is removably secured a tubular cylindrical housing 42. Thehou'sing has a closed forward end wall 44 and has an open rear end 46, which is preferably flush with the rear end of the forepiece 10. i

As shown in FIGURES 4 to 7, a tubular open-ended orifice cylinder 43, substantially shorter than the housing 42, is positioned within the housing, with its forward end 50 abutting the forward end wall of the housing, and with its rear end 52 substantially spaced from the rear end of the housing. The wall of the cylinder 48 is formed, from a point close to its rear end 52, with a forwardly tapered isosceles triangular orifice 54, whose narrow end or apex 56 is substantially spaced from the forward end of the cylinder 48, and is on the longitudinal centerline of the cylinder. The orifice cylinder 48 is held forward in place in the housing 42 by means of a forward snap ring 58, engaging in an annular groove 60, formed in the wall of the housing 42.

A piston 62, which works only in the orifice cylinder 48, is threaded or otherwise suitably secured on the forward end of the piston rod 32, as indicated at 64. A spacer sleeve 66 is circumposed on the piston rod, between the piston 62 and a washer 68,tl1rough which the piston rod can slide. The washer 68 is positioned between the snap ring 58 and the rear end of the orifice cylinder 48. A coil return spring 67 is positioned within the orifice cylinder 48 and is lightly com ressed between the forward end wall 44, of the housing 42, and the forward end of the piston 62, and serves to push the forepiece 10 forwardly after a recoil thereof, to its normal firing position.

A floating tubular packing gland '70, which works only in the housing 42, is slidably circumposed on the piston rod 32 between the forward snap ring 58 and a balancing spring 72. The balancing spring 72 is compressed lightly between the packing gland 70 and a washer 74, which constitutes means closing the rear end of the housing 42 and which is backed up by a rear snap ring 76, engaged in a groove 78, in the wall of the housing 42, at the rear end of the latter. An 0 ring 71 is seated in an external groove 73 in the gland 70.

The bore 39 of the packing gland 70 has a close fit on the piston rod 32, and the contact therebetween is sealed by means of an anular seal 82, compressed in an annular groove 84, formed in the wall of the bore 80. An air bleed passage 86 opens to the side of and to the rear end of the gland 70 and is provided for bleeding air from the orifice cylinder 48 and the housing 42, when assembling the device, after which the rear end of the passage 86 is closed by means of a screw plug 88. Suitable hydraulic fluid (not shown) fills the interior of the orifice cylinder 48 and of the housing 42, between the forward end wall of the housing and packing gland 70, in the normal or starting position of the piston, illustrated in FIGURE 6.

In operation, when the firearm is fired, the stock forepiece moves rearwardly into the bore 14 of the butt piece 12, so that the fluid in front of the piston 62 and the return spring 67 are compressed, by the rearward movement of the housing 42, accompanying the rearward movement of the forepiece 10. As this action commences, the escape of fluid through the orifice 54 is at a maximum because the piston 62 is at the wide rear end of the orifice, and the recoil of the forepiece 10 is given only minimal hydraulic resistance or absorption. As this action proceeds the hydraulic resistance or recoil absorption is gradiently increased, due to the taper, and hence the reduction of the opening of the orifice toward its apex 56, so that kick to the shoulder of the shooter is substantially reduced. In this recoil absorbing action, the return spring :57 provides a gentle cushioning effect, which further reduces the kick of the firearm, and which serves to compress this spring. At the end of recoil action, the balancing spring 72 expands and this and atmospheric pressure serve to push the packing gland 70 forwardly and keep it in effective contact with the hydraulic fluid present within the orifice cylinder 48 and the housing 42, so that the stock forepiece 10 is gently but swiftly pushed out of the butt part 12 to its normal firing position. The spring '72 also serves, on changes of temperature, to compensate for the resultant changes in position of the packing gland 70.

Adjustment of the device to different desired lengths of pull is done simply by disassembling the device only enough to reach and loosen the piston rod lock nut 36, rotating the piston rod 32 in the threaded bore 26 of the anchor plate 18, in the proper direction, and then replacing the removed parts after tightening the lock nut against the rear side of the anchor plate.

In FIGURE 8 is shown another embodiment of the invention, wherein a device similar to that described hereinabove is mounted through the rear end of a firearm gun stock forepiece 10a, and is anchored to the rear wall 90 of a short butt piece 12a, which slides over the rear end of the forepiece.

Important functions of the packing gland 70 and the spring 72 are automatic compensation for expansion and contraction of the fluid, due to temperature changes, with the closed portion of the cylinder completely full of fluid, so that the gun can be carried or fired in any position, without the creation of air bubbles in the mechanism and erratic recoil absorption; and, provision for the piston rod to move rearwardly into the sealed part of the cylinder, despite the presence therein of noncompressible fluid. On this rearward movement of the piston, the packing gland moves rearwardly as the fluid is displaced by the rearward movement of the piston rod.

What is claimed is:

1. A firearm comprising a first member, a second member slidable on the first member, an elongated housing having a closed forward end and an open rear end disposed Within the first member, means closing the rear end of the housing, a cylinder having a front and a rear end positioned within the housing and having the front end abutting against the closed forward end of the housing and having the rear end spaced from the rear end of the housing, a piston rod anchored to the second member and extending through the rear end of the housing into the housing and through the rear end of the cylinder into the cylinder, a piston on the part of the piston rod within the cylinder and working within the cylinder, a return spring in the cylinder between the front end thereof and the piston, a floating packing gland circumposed about the part of the piston rod within the housing and slidable on the piston rod, a balancing spring circumposed about the piston rod and compressed between the packing gland and the rear end of the housing, the space within the cylinder and the part of the housing between the rear end of the cylinder and the packing gland forming a chamber adapted to contain hydraulic fluid, and graduated orifice means on the cylinder adapted to be occulded by the piston for gradiently passing hydraulic fluid from said chamber toward the rear end of the housing past the piston as the second member is moved relative to the first member, and a spacer sleeve circumposed on the piston rod between the piston and said packing gland.

2. A firearm comprising a first member, a second member slidable on the first member, an elongated housing having a closed forward end and an open rear end disposed within the first member, means closing the rear end of the housing, a cylinder having a front and a rear end positioned within the housing and having the front end abutting against the closed forward end of the housing and having the rear end spaced from the rear end of the housing, a piston rod anchored to the second member and extending through the rear end of the housing into the housing and through the rear end of the cylinder into the cylinder, a piston on the part of the piston rod within the cylinder and working within the cylinder, a return spring in the cylinder between the front end thereof and the piston, a floating packing gland circurnposed about the part of the piston rod within the housing and slidable on the piston rod, a balancing spring circumposed about the piston rod and compressed between the packing gland and the rear end of the housing, the space Within the cylinder and the part of the housing between the rear end of the cylinder and the packing gland forming a chamber adapted to contain hydraulic fluid, and graduated orifice means on the cylinder adapted to be occluded by the piston for gradiently passing hydraulic fluid from said chamber toward the rear end of the housing past the piston as the second member is moved relative to the first member, said orifice means comprising a longitudinallytapered opening in the Wall of the orifice cylinder, a forward snap ring on the housing and in retaining relation to the rear end of the orifice cylinder, a spacer sleeve on the piston rod between the piston and the packing gland, said forward snap ring being in stop relation to the rear end of the spacer sleeve.

3. A firearm comprising a first member, a second member slidable on the first member, an elongated housing having a closed forward end and an open rear end disposed within the first member, means closing the rear end of the housing, a cylinder having a front and a rear end positioned within the housing and having the front end abutting against the closed forward end of the housing and having the rear end spaced from the rear end of the housing, a piston rod anchored to the second member and extending through the rear end of the housing into the housing and through the rear end of the cylinder into the cylinder, a piston on the part of the piston rod within the cylinder and working within the cylinder, a return spring in the cylinder between the front end thereof and the piston, a floating packing gland circumposed about the part of the piston rod within the housing and slidable on the piston rod, a balancing spring circumposed about the piston rod and compressed between the packing gland and the rear end of the housing, the space within the cylinder and the part of the housing between the rear end of the cylinder and the packing gland forming a chamber adapted to contain hydraulic fluid, and graduated orifice means on the cylinder adapted to be occluded by the piston for gradiently passing hydraulic fluid from said chamber toward the rear end of the housing past the piston as the second member is moved relative to the first member, said orifice means comprising a longitudinally-tapered opening in the wall of the orifice cylinder, 3. forward snap ring on the housing and in retaining relation to the rear end of the orifice cylinder, a spacer sleeve on the piston rod between the piston and the packing gland, said forward snap ring being in stop relation to the rear end of the spacer sleeve, and a rear snap ring on the housing adjacent to the rear end thereof, said rear snap ring being in retaining engagement with a Washer bridging the rear end of the housing.

References Cited by the Examiner UNITED STATES PATENTS Behr 42--74 Kinkaid 18888.507

Stetson 4274 Peek 188-96.7

Stiefiel 4274 Hoge 42-74 10 BENJAMIN A. BORCHELT, Primary Examiner. 

1. A FIREARM COMPRISING A FIRST MEMBER, A SECOND MEMBER SLIDABLE ON THE FIRST MEMBER, AN ELONGATED HOUSING HAVING A CLOSED FORWARD END AND AN OPEN REAR END DISPOSED WITHIN THE FIRST MEMBER, MEANS CLOSING THE REAR END OF THE HOUSING, A CYLINDER HAVING A FRONT AND A REAR END POSITIONED WITHIN THE HOUSING AND HAVING THE FRONT END ABUTTING AGAINST THE CLOSED FORWARD END OF THE HOUSING AND HAVING THE REAR END SPACED FROM THE REAR END OF THE HOUSING, A PISTON ROD ANCHORED TO THE SECOND MEMBER AND EXTENDING THROUGH THE REAR END OF THE HOUSING INTO THE HOUSING AND THROUGH THE REAR END OF THE CYLINDER INTO THE CYLINDER, A PISTON ON THE PART OF THE PISTON ROD WITHIN THE CYLINDER AND WORKING WITHIN THE CYLINDER, A RETURN SPRING IN THE CYLINDER BETWEEN THE FRONT END THEREOF AND THE PISTON, A FLOATING PACKING GLAND CIRCUMPOSED ABOUT THE PART OF THE PISTON ROD WITHIN THE HOUSING AND SLIDABLE ON THE PISTON ROD, A BALANCING SPRING CIRCUMPOSED ABOUT THE PISTON ROD AND COMPRESSED BETWEEN THE PACKING GLAND AND THE REAR END OF THE HOUSING, THE SPACE WITHIN THE CYLINDER AND THE PART OF THE HOUSING BETWEEN THE REAR END OF THE CYLINDER AND THE PACKING GLAND FORMING A CHAMBER ADAPTED TO CONTAIN HYDRAULIC FLUID, AND GRADUATED ORIFICE MEANS ON THE CYLINDER ADAPTED TO BE OCCULDED BY THE PISTON FOR GRADIENTLY PASSING HYDRAULIC FLUID FROM SAID CHAMBER TOWARD THE REAR END OF THE HOUSING PAST THE PISTON AS THE SECOND MEMBER IS MOVED RELATIVE TO THE FIRST MEMBER, AND A SPACER SLEEVE CIRCUMPOSED ON THE PISTON ROD BETWEEN THE PISTON AND SAID PACKING GLAND. 